A gasification device of this type is known from patent document AT 405937 B. A gasification device of this type can be used to upgrade heterogeneous, biogenic fuels and synthetics and to obtain therefrom a fuel gas with a high calorific value or synthesis gas which is as free from nitrogen as possible, which is suitable for the production of electricity or for the synthesis of organic products. In that respect, the fuel is introduced into a gasification zone constituted as a stationary fluidized bed which is fluidized with steam and/or CO2 and reacted with the fluidization gases or with the gasification agent (steam and/or CO2) and degassed with the aid of heat from the bed material and partially gasified with the exclusion of air. The product gas which rises is then drawn off and the cooled bed material with the non-gasified remaining fuel is fed to the combustion zone via sluice-like devices, such as a constriction. In the combustion zone, the bed material is fluidized with the remaining fuel using air, to form a rapidly moving fluidized bed and the remaining fuel is burned. After extracting the combustion exhaust gas in a cyclone via sluice-like devices, for example a siphon, the bed material is fed to the stationary fluidized bed of the gasification zone.
By using a catalytically active bed material, in particular based on nickel and/or niobium, the gas formed upon degassing and gasification is purified, insofar as practically only CO, CO2 and H2 as the combustible components along with steam are present, or a methane-rich gas with a high calorific value is produced. Furthermore, the gasification temperature can be reduced from approximately 800° C. to 650° C.
The gasification device described in AT 405937 B is suitable for the gasification of carbonaceous material, in particular heterogeneous or biogenic fuels such as biomass, coal, synthetics or pre-sorted rubbish, for example, wherein a mixed gas which contains CO, CO2, H2 and possibly CH4 and higher hydrocarbons is produced. If the gasification takes place entirely in the presence of a nickel or niobium catalyst, then the hydrocarbons such as CH4, for example, are also converted into CO and H2. Avoiding the ingress of air means that a practically nitrogen-free production gas is obtained, which has a high heat value.
Supplying fuel which is usually in the form of bulk material to a gasification reactor is usually carried out with the aid of a mechanical conveying apparatus. In this regard, then, the conveying apparatus must comply with a series of specific demands which are dictated by the gasification reactor. As an example, the conveying apparatus is subjected to a high thermal load because of the temperatures of up to 800° C. prevailing in the gasification reactor, and so care has to be taken to ensure the provision of sufficient cooling for the conveying apparatus. Furthermore, the conveying apparatus has to exclude air so as not to impair the gasification process. In addition, the air must be securely excluded from the conveying apparatus so as not to have a deleterious effect on the gasification process. Furthermore, the construction should be such as to ensure a low level of wear and thus low maintenance costs. Finally, the conveying apparatus should be such as to allow good dosing of the fuel.
In the subject matter of AT 405937 B, conveying into or onto the stationary bed of the gasification zone is carried out with the aid of a screw conveyor. However, this suffers from a series of disadvantages, namely that the screw conveyor is difficult to cool and that, because of the fluctuating degree of filling of the screw, it is difficult to exclude air properly. Furthermore, the screw conveyor is susceptible to breakdowns, which is disadvantageous since the gasification reactor has to be shut down for repair every time it breaks down.